A nonaqueous paint comprises pigment, a resin for forming a coat, and an organic solvent. If the pigment is not dispersed homogeneously in the paint, the pigment aggregates and precipitates while storing the paint for a long time, and it causes a color separation, a color float or a lowering a gloss when painting. Therefore, a dispersant for dispersing the pigment homogeneously is added to the paint.
As such dispersant, (meth)acrylic type block copolymer which (meth)acrylic acid monomer containing amino group or (meth)acrylate containing ammonium group block-polymerizes with (meth)acrylate and macromonomer containing terminal (meth)acryloyl group, is mentioned in Japanese Patent Provisional Publication No. 2002-322226. The amino group or the ammonium group in the copolymer interacts with the pigment strongly, and makes the pigment disperse in the copolymer.
Generally, the dispersant has a pigment affinity part and a resin affinity part, and a basic group or an acidic group acts as the pigment affinity. However, when the dispersant including the basic group is used, the preservation stability of a silanol-including low-pollution type paint falls, or hardening of the baking paint using an acid catalyst is inhibited. On the other hand, when the dispersant including the acidic group with high acid value is used, viscosity of the paint increases, or the preservation stability of the paint falls. In other fields instead of the field of the paint such as an electronic material, addition of dispersant including the acidic group or the basic group tends to be avoided because the charge thereof affects the electronic material.
The present invention has been developed to solve the foregoing problems. It is an object of the present invention to provide a ring-containing modified resin having a benzene ring and/or a condensed ring which has no possibility of affecting stability or hardening of paint and a coating material, as a pigment affinity part. The ring-containing modified resin is used as a dispersant for dispersing the pigment and fine particles sufficiently homogeneously. It is another object of the present invention to provide a dispersant including it.